no.9.c

中南大学C语言程序设计实习 1 实验一：C语言图形模式的设置 2 实习二：一元函数的图形绘制 3 实习三：二维图形的几何变换 4 实习四：非线性方程求根的二分法 5 实习五

#include "stdio.h"
#include "conio.h"

bool curve(float* x, float* y, int n, float* pa, float* pb)
{
    float sx = 0, sy = 0, sxy = 0, sx2 = 0;
    int i;
    
    if ( n < 1 || pa == NULL || pb == NULL ) return false;
    for (i = 0; i < n; i++) {
        sx = sx + x[i];
        sy = sy + y[i];
        sxy = sxy + x[i] * y[i];
        sx2 = sx2 + x[i] * x[i];
    }
    *pa = ( n * sxy - sx * sy ) / ( n * sx2 - sx * sx );
    *pb = ( sy * sx2 - sx * sxy ) / ( n * sx2 - sx * sx );
    return true; 
}

void print(float a, float b)
{
    printf("y = (%.2f)x + (%.2f) \n", a, b);
}

int main()
{
    float a, b;
    float x1[5] = {1, 2, 3, 4, 5};
    float y1[5] = {0, 2, 2, 5, 4};
    float x2[10] = {1.04, 1.80, 1.90, 1.77, 1.47, 1.34, 1.50, 1.91, 2.04, 1.21};
    float y2[10] = {100, 200, 210, 185, 155, 135, 170, 205, 235, 125};
    if ( curve(x1, y1, 5, &a, &b) ) print(a, b);
    if ( curve(x2, y2, 10, &a, &b) ) print(a, b);
    getch();
    return 0;
}